The crewstation instrumentation panels for commercial and military aircraft, naval vessels and tracked and armored vehicles, like many other display systems, frequently employ illuminated indicators and controls (e.g., pushbutton switches). A voltage controlled dimming driver circuit for light emitting diode (LED) illuminated switches
Pushbutton switches with voltage-controlled dimming light emitting diode driver circuits are described, for example, in U.S. Pat. Nos. 5,929,568, 6,323,698, 6,489,728, 6,650,064, 6,653,798, 6,670,776, 6,737,814, 7,126,290, 7,157,859, and 7,202,608, the content of all of which are incorporated herein by reference. However, many of the designs disclosed therein suffer from power inefficiencies, particularly at high applied input voltages. In addition, none of the designs allow operation based on direct current (DC) applied input voltages of either polarity.
There is, therefore, a need in the art for improved power efficiency and dual polarity operation in a voltage-controlled dimming light emitting diode driver circuit.